Alabama has the widest drug-free zones in the country; does this make them ineffective?

Following the legal challenge on eights amendment grounds, a new article discusses drug free zones:

In Alabama, if a person is caught distributing drugs within a 3 mile radius of a school, there is imposed an additional penalty :

In addition to any penalties heretofore or hereafter provided by law for any person convicted of an unlawful sale of a controlled substance, there is hereby imposed a penalty of five years incarceration in a state corrections facility with no provision for probation if the situs of such unlawful sale was on the campus or within a three-mile radius of the campus boundaries of any public or private school, college, university or other educational institution in this state.

(There is another one too for sales which occur within a three-mile radius of a public housing project owned by a housing authority. § 13A-12-270) For many cities in rural Alabama, the entire city is encompassed with the drug free zones. Like Tennessee,

Data obtained from the Tennessee government show there are 8,544 separate drug-free school zones covering roughly 5.5 percent of the state’s total land area. Within cities, however, the figures are much higher. More than 27 percent in Nashville and more than 38 percent in Memphis are covered by such zones. They apply day and night, whether or not children are present, and it’s often impossible to know you’re in one.

 In fact

Alabama has the widest drug-free zones in the country, extending three miles from schools, colleges, and housing complexes. Drug offenses inside those areas carry a five-year enhanced sentence. In practice, this means that 38,267 square miles of Alabama—73 percent of the state—are within a -drug-free zone. Cities with a higher concentration of schools and public housing projects are worse. Ninety-four percent of Montgomery falls within a drug-free zone.

Are these statutes effectively capturing those selling drugs to children:

Drug-free school zone laws are rarely if ever used to prosecute sales of drugs to minors. Such cases are largely a figment of our popular imagination—a lingering hangover from the drug war hysteria of the 1980s. Yet state legislatures have made the designated zones both larger and more numerous, to the point where they can blanket whole towns. In the process, they have turned minor drug offenses into lengthy prison sentences almost anywhere they occur.